Siliguri College

Shiliguri, India

Siliguri College

Shiliguri, India
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Mallik A.,Siliguri College | Barik A.K.,St Pauls Cathedral Mission College | Pal B.,St Pauls Cathedral Mission College
RSC Advances | Year: 2017

Transparent oxyfluoride glass-ceramics of heavy metals doped with rare earth metal ions are important materials in optoelectronics. In the present study, we report the preparation of a glass and a glass-ceramic with composition 16.52Al2O3·1.5 AlF3·12.65LaF3·4.33Na2O·64.85 SiO2 (mol%), where both the materials were doped with 1 mol% Pr2O3. All four species were structurally characterized by Transmission Electron Microscopy (TEM). Pr2O3 affected the phase separation in the glass and deferred crystallization compared to the undoped glass. The crystallization mechanism and the location of various components in the glass/glass-ceramics were ascertained through advanced STEM/EDX techniques. The phase separated regions in the mother glass were mostly populated by F and La and also by Pr, Al and Si. The phase separated droplets, after annealing, turned into 10-20 nm LaF3 nanocrystals, which were found to partly include the doping Pr3+ ions in the crystals themselves. The interphase crystal/glassy matrix was thoroughly characterized by EDX. The results suggest that the inner LaF3 crystal core is engulfed by an Al enriched layer that follows a Si enriched surrounding shell as the outer core. This finding also indicates that the crystal surface is too viscous to further enhance the crystal growth, and therefore the overall crystal formation is limited to the nanosize. © The Royal Society of Chemistry.

Mallik A.,Siliguri College | Barik A.K.,St Pauls Cathedral Mission College | Pal B.,St Pauls Cathedral Mission College
Journal of the European Ceramic Society | Year: 2017

Crystallization, microstructure and mechanical behavior of strontium fluorphlogopite glass-ceramics, SrO·4MgO·Al2O3·6SiO2·2MgF2, was studied by varying the fluorine content. A number of glass-ceramics of each glass batch with excess MgF2 [SR0 (0% MgF2), SR5 (5% MgF2) and SR10 (10% MgF2)] were prepared by heating at its respective nucleation temperature followed by at different crystallization temperatures (780–1150 °C). Differential Thermal Analysis (DTA), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Micro Hardness Indenter were used to study the crystallization, microstructure and mechanical behavior of resulting three glass batches. DTA analysis revealed that the peak crystallization (Tp) and glass transition (Tg) temperatures decreased with increasing fluorine content that also lowers down the activation energy (E) as evident from crystallization kinetics. Hardness and fracture toughness values are higher for less fluorine containing glass-ceramics when they are treated isothermally. However, more fluorine based glass-ceramics is found to be more machinable than the less fluorine one. © 2016 Elsevier Ltd

Neogi D.N.,North Bengal University | Biswas A.N.,Siliguri College | Das P.,North Bengal University | Bhawmick R.,North Bengal University | Bandyopadhyay P.,North Bengal University
Journal of Organometallic Chemistry | Year: 2013

At room temperature, complex [Pt (η3-C4H 7)Cl]2 or [K2PtCl4] regiospecifically activates the C2(naphthyl)-H bond of 2′- alkylthiophenylazo-1-naphthalenes (1, HL) and affords green cycloplatinates [PtIILCl] (2). The structure of platinum(II) cycloplatinate (2a) has been established by single-crystal X-ray crystallography. The platinum(II) centre is surrounded by a tridentate [C,N,S] ligand frame (L) and chloride ion in a distorted square planar fashion. The platinum(II) cycloplatinate (2a) contains a five-membered carboplatinacycle along with a five-membered (N,S) chelate ring. The cycloplatinates [PtIILCl] readily react with halogens X2 (X = Cl, Br, I) and afford blue violet platinum(IV) cycloplatinates [PtIV(C,N,S)X3] (3-5). Methyl iodide (CH3I) reacts with [PtIILCl] and produces [Pt IILI] (6a & 6b). The structures of platinum(IV) cyclometallates (3a & 4b) have been determined by single crystal X-ray crystallography. Time dependent density functional study (TD-DFT) of representative cycloplatinates has been undertaken. The simulated optical spectra of the cycloplatinates are in good agreement with the experimentally observed spectra of the corresponding cycloplatinates. © 2012 Elsevier B.V. All rights reserved.

Kejriwal A.,North Bengal University | Bandyopadhyay P.,North Bengal University | Biswas A.N.,Siliguri College
Dalton Transactions | Year: 2015

In biology, aromatic hydroxylation is carried out using a family of heme and nonheme oxygenases, such as cytochrome P450, toluene monooxygenases (TMOs), and methane monooxygenase (MMO). In contrast, a vast majority of synthetic iron based catalysts employed so far in aromatic hydroxylation are monomeric in nature. Herein, we have employed a diferric complex of an aminopyridine ligand ([(bpmen)2Fe2O(μ-O)(μ-OH)](ClO4)3 (2), bpmen = N,N′-dimethyl-N,N′-bis(2-pyridylmethyl)-1,2-diaminoethane) towards aromatic hydroxylation with H2O2 and acetic acid. The diiron(iii) complex shows promising reactivity in the hydroxylation of benzene and alkylbenzenes with a higher selectivity towards aromatic ring hydroxylation over alkyl chain oxidation. The μ-oxo diiron(iii) core has been shown to be regenerated at the end of catalytic turnover. However, mechanistic studies indicate that the diiron(iii) complex undergoes dissociation into its monomeric congener and the resulting iron(iii) complex mitigates aromatic hydroxylation. © The Royal Society of Chemistry 2015.

Pariyar A.,North Bengal University | Bose S.,North Bengal University | Biswas A.N.,Siliguri College | Das P.,North Bengal University | Bandyopadhyay P.,North Bengal University
Catalysis Communications | Year: 2013

The catalytic properties of 5,10,15-tris(difluorophenyl)iron(IV) corrole complex [(tdfc)FeIVCl] (1) with tert-butylhydroperoxide as the terminal oxidant was evaluated. The 1/t-BuOOH system has been found to catalyze the oxidation of alkanes, alkenes, alkylbenzene and alcohols at room temperature. The homolytic cleavage of the OO bond of tert-butylhydroperoxide by catalyst 1 was observed and the oxygenates have been shown to be derived from organoperoxides. Selective hydroxylation of unactivated CH bonds of alkanes has also been realized using catalyst 1 with m-chloroperbenzoic acid as the oxidant. © 2012 Elsevier B.V.

Pariyar A.,North Bengal University | Bose S.,North Bengal University | Chhetri S.S.,North Bengal University | Biswas A.N.,Siliguri College | Bandyopadhyay P.,North Bengal University
Dalton Transactions | Year: 2012

Selective detection of Hg(II) ions in solution by a series of novel free base bis-(nitrophenyl) corroles (1-4) with general formula A 2B (where A = nitrophenyl, and B = N,N-dimethylaminophenyl, thienyl, naphthyl and tridecyloxyphenyl group) is described. Among the free base corroles, 4, with a tridecyloxy long chain moiety, has been found to exhibit the highest Hg(II) sensing ability. The detection is based on the fluorescence quenching of the corroles, arising from the combined effect of static (coordination) and dynamic (exciplex formation) factors. © The Royal Society of Chemistry 2012.

Bose S.,North Bengal University | Pariyar A.,North Bengal University | Biswas A.N.,Siliguri College | Bandyopadhyay P.,North Bengal University
Journal of Molecular Catalysis A: Chemical | Year: 2013

Metallocorrole catalyzed epoxidation of a series of olefins has been carried out in ionic liquid medium at room temperature with different terminal oxidants. The product selectivity achieved in ionic liquid medium shows remarkable improvement over those obtained in common organic solvents. © 2013 Elsevier B.V. All rights reserved.

Sen S.K.,Siliguri College | Mandal P.,North Bengal University
Journal of Central European Agriculture | Year: 2016

The objective of present study was to evaluate the response of the mung bean seeds of ‘Sonali B1’ variety primed with chitosan in four different concentrations (0, 0.1%, 0.2% and 0.5%) under salinity stress of five different concentrations (i.e., 0, 4, 6, 8 and 12 dS*mm-1) and halotolerance pattern by applying Celite as matrix at three different moisture levels (5%, 10% and 20%). Improved germination percentage, germination index, mean germination time, coefficient of velocity of germination along with root and shoot length was observed comparing with control. Germination stress tolerance index (GSI), plant height stress tolerance index (PHSI) and root length stress tolerance index (RLSI) were used to evaluate the tolerance of the mung bean seeds against salinity stress induced by chitosan. Results of GSI, PHSI, RLSI showing noteworthy inhibitory effect of salinity stress in control set was significantly less pronounced in chitosan treated seedlings. Chitosan can remarkably alleviate the detrimental effect of salinity up to the level of 6 dS*m-1, beyond which no improvement was noticed. In conclusion present investigation revealed that chitosan is an ideal elicitor for enhancing the speed of germination and seedling invigoration that synchronize with emergence of radicle and salinity stress tolerance. © 2016, University of Zagreb - Faculty of Agriculture. All rights reserved.

De A.,Siliguri College | Roy A.,University of Calcutta
Journal of Engineering Mathematics | Year: 2012

An earthquake source has been simulated as a simple finite source, i. e., normal pressure acting over an inclined fault plane. The transient response of the surface displacement of an elastic half space due to the above internal source is calculated. A series of transformations, followed by the traditional Cagniard-de Hoop technique, are used to compute the transient response. Various wave arrivals are discussed. Numerical computations bring out the special character of the finite source vis-à-vis the point source. The originality of the paper lies in the fact that for the first time an exact computation of the surface response due to an inclined finite source has been computed by Cagniard's approach. © 2011 Springer Science+Business Media B.V.

De A.,Siliguri College
Wave Motion | Year: 2014

The application of the property of dynamic similarity is useful to the solution which admits a self-similarity or homogeneous form. One independent variable has been dropped in the present equivalent set of the governing equations. The displacement discontinuity on the crack face and also the displacement field on the surface due to an in-plane shear model over an expanding zone of slippage of arbitrary dip have been obtained. The moving slip edge extends towards the surface with a constant velocity. Cagniard De-Hoop technique has been used here to obtain the two dimensional exact transient response due to the slip in the vertical mode via body force equivalent. The results of the present paper are valid at least up to the time when the diffracted waves from the crack edge have not reached the receiving station. The spectral behavior of the source time function has also been discussed. © 2014 Elsevier B.V.

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